1. Field of the Invention
The invention relates to an image forming process, a toner, and an apparatus for carrying out the process such as a copier, a printer, a fax and a multifunctional machine using toner particles.
2. Description of the Related Art
Japanese Laid-Open Patent Publication No. 2004-145260 discloses an image forming apparatus including at least a latent image carrier, a developing device that develops latent images on the latent image carrier to toner images, an intermediate transfer body to which developed toner images are transferred from the latent image carrier, an transferring-and-fixing body to which toner images are transferred from the intermediate transfer body, a heater to heat toner images on the transferring-and-fixing body, a pressure body pressing to the transferring-and-fixing body in order to transfer and fix toner images on the transferring-and-fixing body to a paper moving between the transferring-and-fixing body and the pressure body, and a cleaner to clean residual toner images from the transferring-and-fixing body after fixing process.
In this type of image forming apparatus, since toner particles are transferred and fixed to a paper after it is heated, it is not necessary to heat the paper with temperature as high as that of a conventional image forming apparatus in which toner particles are heated on a paper. Thus, toner particles can be fixed to a paper with less heat and energy saving can be achieved.
However, there is a feature in this type of image forming apparatus that heat on the heated transferring-and-fixing body may transfer to toner particles in the developing device by way of the intermediate transfer body and the latent image carrier. If the heat is high enough soften toner particles in the developing device, softened toner particles will adhere to the surface of the latent image carrier to form a film of toner material thereon. This situation is called “toner filming”. Once toner filming occurs, the quality of toner images on the latent image carrier deteriorates and so do toner images on a paper.
One possible solution to suppress this “toner filming” is to reduce the temperature of the transferring-and-fixing body after fixing so that the amount of heat transferred from the transferring-and-fixing body to the intermediate body is reduced. If the amount of heat transferring from the transferring-and-fixing body to the intermediate body is reduced, the rise of the temperature of toner particles in the developing device is reduced and toner filming is reduced.
However, if the temperature of residual toner particles on the transferring-and-fixing body is too low, it becomes difficult to remove residual toner particles by the cleaner because the viscosity of any residual toner particles becomes higher under low temperature.
If unremoved residual toner particles remain on the transferring-and-fixing body, those toner particles may adhere to a paper at next image forming process and the image on a paper may be contaminated.
This contamination can be improved by keeping the temperature of the transferring-and-fixing body and residual toner particles high after the fixing process. However, if the temperature is kept high, the “toner filming” may occur as mentioned above.
On the other hand, Japanese Laid-Open Patent Publication No. H10-63121 discloses an image forming apparatus including at least a latent image carrier, a developing device that develops latent images on the latent image carrier to toner images, an intermediate transfer body to which developed toner images are transferred from the latent image carrier, a heater to heat toner images on the intermediate transfer body, a pressure body pressing to the intermediate transfer body in order to make toner images on the intermediate transfer body be transferred and fixed to a paper moving between intermediate transfer body and the pressure body, and a cleaner to clean residual toner images from the intermediate transfer body after fixing process.
This type of image forming apparatus is almost the same as the previous one, except there is no transferring-and-fixing body. Toner images on the intermediate transfer body are heated and softened by the heater. Softened toner images are transferred to a paper and simultaneously fixed to the paper.
This type of image apparatus has the same merits and demerits as previously explained for the image forming apparatus. Lowering the temperature of the intermediate transfer body and residual toner images after the transfer process results in the decline of cleanability of the intermediate transfer body. Keeping temperature of the intermediate transfer body and residual toner images high results in the toner filming on the latent image carrier and decline of the image quality.